Rob Lewis

Fabrication of a multi-octave phased array aperture

A wide band planar phased array antenna consisting of 21 by 21 Highly-Coupled Dipole (HCD) elements was designed using a combination of the ‘AGATE’ in-house FDTD based prediction tool and commercial microwave circuit design software. This paper discusses the challenges presented during the manufacture of this array antenna, specifically the impact of practical manufacturing considerations and their influence on the design, and the effect of manufacturing variations, relative to the ‘ideal’ design, on the performance of the antenna as produced.

Phased array system consisting of unit pattern reconfigurable Square Loop Antennas

A 2×2 array of pattern adaptive Square Loop Antennas (SLA) is presented. The antenna generates off-boresight tilted beams (14.4dBi at θ_max =32°) in four different quadrant of Φ_max=45°, Φ_max=135°, Φ_max=225° and Φ_max=315°, when four of its feeding ports are excited by proper phases. The antenna also provides both circularly and linearly polarized axial beams (13.6dBi) when all the 16 feeding ports are excited simultaneously with specific phases. These five distinct patterns enable systems to offer high gain coverage in both off-boresight and boresight directions.

Wideband antenna technology in military applications

Wideband antennas are essential for military systems requiring spectrum-agility or multi-functionality. High-gain radar or communication systems require wideband, potentially multi-octave, radiation patterns and VSWR, sometimes with wide angle scanning. Aperture size is constrained by the dimensions of the host platform (e.g. aircraft or naval ship). Low gain mobile communication systems require wideband VSWR but have simpler radiation pattern requirements. Body-worn antennas can be integrated into clothing and are emerging in military communications, with dimensions constrained by those of the human body. Here we describe technologies for two military applications.

Planar pattern reconfigurable antenna integrated with a WiFi system for multipath mitigation and sustained high definition video networking in a complex EM environment

A planer pattern reconfigurable square loop antenna integrated in a complete wireless system is presented. The antenna is designed to operate at 5 GHz WiFi band of IEEE 802.11 ac. The antenna under electronic switching generates four tilted beams in the four space quadrants. These four beams are moved intelligently and automatically in space using a C# program for achieving and sustaining maximum possible throughput. This auto beam steering is advantageous for scenarios where a mobile user suffers from multipath fading in a complex electromagnetic environment.

Reconfigurable phased array antenna enabling a high gain wide angle beam scanning

A 2×2 phased array antenna consisting of pattern reconfigurable Square Loop Antennas (SLAs) is presented for high gain wide angle scanning. The single element SLA works in two modes. The first is the tilted beam mode in which it can generate four tilted beams in four quadrants and the second mode is the axial radiation mode. In this paper, it is demonstrated that by combing these two modes, a 2×2 array of SLA is capable of providing high-gain wide-angle beam scanning. It is expected that in comparison with the conventional 2×2 patch array antenna the SLA array can offer a 75% wider scanning angle with gain up to 6 dB higher in the off bore sight direction. This property could be of a huge significance for scanning the wide sky for airborne and marine applications.

A conformal pattern adaptive Square Loop Antenna for body and vehicle platforms

A beam steerable Square Loop Antenna (SLA) on a ~λ0/10 substrate has been designed for conformal platforms. The curving is done on a symmetric spherical surface and its effect on antenna performance is analyzed. The bend limit to which the antenna retains beam adaptive characteristics is reported. The SLA has four feeds and generates a tilted beam which can be steered in space using simple RF switches. Compared to the earlier reported work on non-EBG / non-capacitive fed antenna this SLA effectively is 44 % thinner, has 1.2 dB higher gain and operates at 36.5 % lower frequency.

Vox, video and data sharing using body worn antennas

A wireless network integrated in the current ‘multicam’ uniform worn in operational environments by the British Army is described, based on body worn antennas and 802.11n network technology, for communication within patrols. The antennas are lightweight, flexible, robust, and contain a novel integrated balun, which together with the antenna design, permits function over very wide (6:1) bandwidths. A match of better than 1.67:1 VSWR from 800MHz to 5GHz was found to be typical, much larger than was required to support the 29.5Mb/s data rate. The network is capable of sharing voice, video from helmet mounted cameras on individual soldiers or fixed surveillance equipment, and data such as GPS derived positional information, the user simply selecting the required information feed via a wrist mounted smart phone. This additional functionality, relative to existing radios, leads to improved situational awareness for patrol members, individually and collectively.

Design of a multi-octave balun for phased array antennas

In the drive for the development of wideband array antennas for military applications, a well designed balun is essential to achieve overall antenna performance. However, for balanced antenna arrays to be driven effectively, antiphase element feeds are required at the correct impedance over multiple octaves. This paper summarises balun design options in microstrip and stripline for use with highly coupled dipoles giving a 4:1 bandwidth from 2.7–10.8GHz.